Overview
- A paper led by Dr. Gaku Nishiyama published Monday reports that applying a surface‑roughness correction to MESSENGER data raises Mercury’s radial contraction from about 8.3 km to roughly 11.6 km.
- The team mapped global roughness from MESSENGER topography and found cataloged contractional faults appear mainly in smoother areas, suggesting heavily cratered terrain has concealed many shortening structures.
- The authors estimate prior tectonic maps may have underestimated contraction by roughly 10–30 percent, which corresponds to as much as about 14.5 miles of lost diameter over Mercury’s history.
- That larger shrinkage alters models of Mercury’s interior by favoring thinner regolith, different cooling rates and lower light‑element content in the core, and the authors stress the revised number is likely a lower bound.
- Definitive testing will come from ESA–JAXA’s BepiColombo laser altimeter, whose ≈100‑meter topography should reveal whether masked faults exist in rough regions and whether the same bias affects the Moon or Mars.